(a) Field of the Invention
The present invention relates to a stent, and more particularly, to a stent which can be easily pushed out of an introducer when it is introduced into an internal wall by a pusher.
(b) Description of the Related Art
Generally, a stent is introduced into a stricture portion of an internal wall such as a blood vessel, a bilious track, and an esophagus to enlarge the stricture portion of the internal wall and maintain the enlarged stricture portion.
Such a stent is cylindrical and self-expandable so that it can be contracted by outer force. The self-expandable stent is classified into a spiral type and a zig-zag type.
The zig-zag type stent comprises a plurality of turns made of a wire having a unit length. Each of the turns comprises a plurality of straight sections joined one another by a plurality of bending points such that it has a plurality of valleys and peaks. The valleys of a turn are interlocked with peaks of an adjacent turn.
To dispose the stent on the stricture portion of the internal wait, the stent is first contracted in the smaller diameter and inserted in an introducer. In this state, the introducer is inserted into the internal wall and the stent is pushed out of the introducer by a pusher so that it is located on the internal wall, while being extended lengthwise.
However, since the turns are connected to each other at the valleys and peaks, the sufficient pushing force cannot be obtained when the stent is pushed by the pusher. In addition, a size of each mesh formed by the connection of the valleys and peaks is so large, the flexibility of the stent is deteriorated, and the cancer can be easily penetrated into the stent through the mesh.
Furthermore, since the conventional stent is simply formed in the cylindrical shape, it may be displaced from the desired location to other portion.
Therefore, the present invention has been made in an effort to solve the above problems.
It is an objective of the present invention to provide a stent which can be easily pushed out of an introducer when it is located in an internal wall.
It is another objective of the present invention to provide a stent that can be designed such that a size of meshes can be minimized, while increasing the number of meshes.
It is still another objective of the present invention to provide a stent that can be prevented from being moved in a state where it is disposed in the internal wall.
To achieve the above objectives, the present invention provides a stent comprising a first turn made of a wire having a unit length, the first turn being formed having a plurality of first straight sections connected to each other by a plurality of bending points along a circumferential plane and a plurality of valleys and peaks formed by the bending points; and a first intersection turn made of a wire having a unit length, the first intersection turn being formed having a plurality of straight sections intersecting the first straight sections to form a plurality of meshes, the straight sections of the intersection turn formed by a plurality of peaks and valleys.
The stent may further comprise a second turn and a second intersection turn, the valleys of the first turn being interlocked with peaks of the second turn, the valleys of the first intersection turn being interlocked with the peaks of the second intersection turn.
One of the straight sections of the first intersection turn is twisted on one of the straight sections of the first turn at least more than one time.
One of the straight sections of the first intersection turn is twisted on intersection points of the straight sections of the first turn and the first intersection turn.
The first turn and the first intersection turn are formed in an identical cycle. The first turn and the first intersection turn are formed having an identical width to each other.
One of the first turn and the first intersection turn comprises an anti-migration turn for preventing the stent from being moved out of a desired portion of an internal wall.
The anti-migration turn comprises a flare turn formed on one end of one of the first turn and the first intersection turn, a diameter of the fare turn being increasingly increased from the one end.